International Journal of Comparative Psychology

The study of behavioural gender differences among Callitrichid primates

has been generally neglected. We describe evidence from experimental studies in

which adult female tamarins (Saguinus) and marmosets (Callithrix) demonstrate priority

of access to food that is spatially and temporarily restricted. Differences in behavioural

strategies between both reproductive and non-reproductive females, and males, are

consistent with differences between the genera in their feeding ecology and social

organisation. They are also functionally plausible. A recent study gives preliminary

data to show that, although mated females in family groups of common marmosets

demonstrate priority of access to food sources, overall there are differences in

responsiveness that may be influenced by factors such as the time of feeding, energy

content and preference of food.

Intra- and inter-specific social learning was investigated in two species of

New World monkey, the saddle-backed tamarin {Saguinus fuscicoUis) and the redbellied

tamarin {S. labiatus), which form stable and permanent mixed-species troops in

the wild. We explored whether improved food acquisition, through social learning, is a

potential advantage of mixed-species troop formation by allowing a pair of naive

observers to watch a pair of trained demonstrators complete a novel foraging task. The

aims of the study were (a) to determine if individuals succeeded at the task more

quickly after having observed demonstrators, (b) to investigate whether speed of

acquisition differed after observation of conspecific demonstrators as opposed to

congeneric demonstrators, and (c) to compare performance between species. The

number of trials taken by observers to succeed on the task was compared with that taken

by naive demonstrators to succeed on the task initially. Individuals succeeded on the

task more quickly if they had had the opportunity to watch demonstrators perform the

task, regardless of whether the demonstrator was a conspecific or congeneric. There was

no difference in performance between species. It is concluded that, for both species, the

learning of a new foraging technique is facilitated by the presence of both conspecifics

and congenerics and that the likely mechanism for this facilitation is a combination of

stimulus enhancement and response facilitation. Social learning of this kind is discussed

with respect its adaptive value in wild mixed-species tamarin troops.

Age, hand preference and gender are shown to be associated with

exploration behaviour performed by Callithrix jaccfius, depending on the context in

which the marmosets are tested. When each marmoset was tested alone in a novel

environment, hand preference had a significant effect on exploration: right-handed

marmosets explored more actively than left-handed ones. This difference is probably

related to hemispheric specialisation for processing novel stimuli and controlling

emotional responses. Age and gender were found to have no significant effect on

exploration in this context. When the marmosets were tested in the social groups and by

placing novel objects in their home cages, both hand preference and age influenced

approach and interaction with the stimuli, but again gender had no significant effect.

Solving a novel problem in the home cage was influenced only by age, or related social

dominance, and not by gender or hand preference. The implications of these results to

behaviour of wild marmosets and other species are discussed.